doc: arch: semihost: Add Xtensa support

Add information about Xtensa semihosting.

Signed-off-by: Tahsin Mutlugun <Tahsin.Mutlugun@analog.com>

Author: ttmut

doc/hardware/arch/semihost.rst

@@ -6,16 +6,19 @@ Semihosting Guide
 Overview
 ********
 
-Semihosting is a mechanism that enables code running on ARM and RISC-V targets
-to communicate and use the Input/Output facilities on a host computer that is
-running a debugger or emulator.
+Semihosting is a mechanism that enables code running on ARM, RISC-V and Xtensa
+targets to communicate and use the Input/Output facilities on a host computer
+that is running a debugger or emulator.
 
 More complete documentation on the available functionality is available at the
 `ARM Github documentation`_.
 
 The RISC-V functionality borrows from the ARM definitions, as described at the
 `RISC-V Github documentation`_.
 
+Semihosting implementation on Xtensa supports GDB File-I/O extension, which is
+explained in `GDB File-I/O Remote Protocol`_.
+
 File Operations
 ***************
 
@@ -66,3 +69,4 @@ API Reference
 
 .. _ARM Github documentation: https://github.com/ARM-software/abi-aa/blob/main/semihosting/semihosting.rst
 .. _RISC-V Github documentation: https://github.com/riscv/riscv-semihosting-spec/blob/main/riscv-semihosting-spec.adoc
+.. _GDB File-I/O Remote Protocol: https://sourceware.org/gdb/current/onlinedocs/gdb.html/File_002dI_002fO-Remote-Protocol-Extension.html